Lepospondyli is a diverse taxon of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco, lepospondyls lived from the Early Carboniferous (Mississippian) to the Early Permian and were geographically restricted to what is now Europe and North America. Five major groups of lepospondyls are known: Adelospondyli; Aïstopoda; Lysorophia; Microsauria; and Nectridea. Lepospondyls have a diverse range of body forms and include species with newt-like, eel- or snake-like, and lizard-like forms. Various species were aquatic, semiaquatic, or terrestrial. None were large, and they are assumed to have lived in specialized ecological niches not taken by the more numerous temnospondyl amphibians that coexisted with them in the Paleozoic. Lepospondyli was named in 1888 by Karl Alfred von Zittel, who coined the name to include some tetrapods from the Paleozoic that shared some specific characteristics in the notochord and teeth. Lepospondyls have sometimes been considered to be either related or ancestral to modern amphibians or to Amniota. It has been suggested that the grouping is polyphyletic, with aïstopods being primitive stem-tetrapods, while recumbirostran microsaurs are primitive reptiles.
Reptiliomorpha is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was defined by Michel Laurin (2001) and Vallin and Laurin (2004) as the largest clade that includes Homo sapiens, but not Ascaphus truei. Laurin and Reisz (2020) defined Pan-Amniota as the largest total clade containing Homo sapiens, but not Pipa pipa, Caecilia tentaculata, and Siren lacertina.
Anthracosauria is an order of extinct reptile-like amphibians that flourished during the Carboniferous and early Permian periods, although precisely which species are included depends on one's definition of the taxon. "Anthracosauria" is sometimes used to refer to all tetrapods more closely related to amniotes such as reptiles, mammals, and birds, than to lissamphibians such as frogs and salamanders. An equivalent term to this definition would be Reptiliomorpha. Anthracosauria has also been used to refer to a smaller group of large, crocodilian-like aquatic tetrapods also known as embolomeres.
Nectridea is the name of an extinct order of lepospondyl tetrapods from the Carboniferous and Permian periods, including animals such as Diplocaulus. In appearance, they would have resembled modern newts or aquatic salamanders, although they are not close relatives of modern amphibians. They were characterized by long, flattened tails to aid in swimming, as well as numerous features of the vertebrae.
Embolomeri is an order of tetrapods or stem-tetrapods, possibly members of Reptiliomorpha. Embolomeres first evolved in the Early Carboniferous (Mississippian) Period and were the largest and most successful predatory tetrapods of the Late Carboniferous (Pennsylvanian) Period. They were specialized semiaquatic predators with long bodies for eel-like undulatory swimming. Embolomeres are characterized by their vertebral centra, which are formed by two cylindrical segments, the pleurocentrum at the rear and intercentrum at the front. These segments are equal in size. Most other tetrapods have pleurocentra and intercentra which are drastically different in size and shape.
The Stereospondyli are a group of extinct temnospondyl amphibians that existed primarily during the Mesozoic period. They are known from all seven continents and were common components of many Triassic ecosystems, likely filling a similar ecological niche to modern crocodilians prior to the diversification of pseudosuchian archosaurs.
Chroniosuchidae is a family of semi-aquatic tetrapods found in sediments from the upper Permian and the upper Triassic periods, most in Russia. They were generally rather large animals, with long jaws similar to those found in modern crocodiles, and probably lived a similar life style as riverside piscivores and ambush predators. Like all Chroniosuchians, they bore extensive osteoderm armour on their backs, possibly as protection against terrestrial predators such as the Permian therapsids and the Triassic Rauisuchians.
Chroniosuchus is an extinct genus of chroniosuchid from the upper Permian period. The genus was first named by Vjuschkov in 1957.
Uralerpeton is an extinct genus of chroniosuchid reptiliomorph from upper Permian deposits of Vladimir Region, European Russia. It was first named by V. K. Golubev in 1998, from skull fragments and trunk scutes. The type species is Uralerpeton tverdokhlebovae, it was a large predator with a 50 – 55 cm skull and a total length that probably exceeded 3 m (9.3 ft).
Chroniosaurus is an extinct genus of chroniosuchid reptiliomorph from upper Permian deposits of Novgorod, Orenburg and Vologda Regions, Russia. It was first named by Tverdokhlebova in 1972 and the type species is Chroniosaurus dongusensis.
Bystrowiana is an extinct genus of bystrowianid chroniosuchian from upper Permian deposits of Vladimir Region, Russia and Jiyuan, China. Chroniosuchians are often thought to be reptiliomorphs, but some recent phylogenetic analyses suggest instead that they are stem-tetrapods. The genus is named in honour of the Russian paleontologist Alexey Bystrow. It was first described by Vyushkov in 1957 and the type species is Bystrowiana permira. Two species—B. permira and B. sinica—are known.
Kotlassia extinct genus of kotlassiine seymouriamorph from the Late Permian of Russia. The type, and currently only, species is K. prima.
Madygenerpeton is an extinct genus of chroniosuchid reptiliomorph from the Late Triassic Madygen Formation of Kyrgyzstan. It was first named by paleontologists Rainer R. Schoch, Sebastian Voigt and Michael Buchwitz in 2010 from a nearly complete skull and associated osteoderms. The type species is M. pustulatus.
Suchonica is an extinct genus of chroniosuchid reptiliomorph from upper Permian deposits of Sukhona Formation of Vologda Region, Russia. It was first named by V. K. Golubev in 1999, from the anterior armor scute. The type species is Suchonica vladimiri.
Jarilinus is an extinct genus of chroniosuchid reptiliomorph from upper Permian deposits of Novgorod and Orenburg Region, Russia. It was first named by V. K. Golubev in 1998, from skull fragments and trunk scutes. The type species is Jarilinus mirabilis.
Velosauria is a group of pareiasaur reptiles that existed in the late Permian period. They ranged in size from the 50-centimeter-long Pumiliopareia to the 3-meter-long Scutosaurus. Velosaurs were some of the largest reptiles of their time.
Bystrowianidae is a family of chroniosuchian tetrapods from the Permian and Triassic periods.
Rhachitomi is a group of temnospondyl amphibians that includes all temnospondyls except edopoids and dendrerpetontids. It was established as a clade name by German paleontologist Rainer R. Schoch in 2013, although the name had first been established in 1919 by British paleontologist D. M. S. Watson to encompass an evolutionary grade of temnospondyls leading to the group Stereospondyli. American paleontologist Alfred Romer used the term in a similar sense, grouping most Permian and Triassic temnospondyls under Rhachitomi. A similar name that appeared earlier in the scientific literature is Rachitomi, which was named by American paleontologist Edward Drinker Cope in 1882. Rachitomi was commonly used in the late nineteenth and early twentieth century to include early amphibians such as Eryops and Archegosaurus that had rhachitomous vertebrae. Many early tetrapods have vertebrae that are split into two parts below the notochord: a pleurocentrum and an intercentrum. In rhachitomous vertebrae, the intercentrum is large and semicircular, while the pleurocentrum divided into two smaller paired elements. Schoch defined Rhachitomi as a node-based taxon to include four major and well-supported clades of temnospondyls: Dvinosauria, Eryopidae, Stereospondyli and a clade formed by Zatracheidae and Dissorophoidea. Not all members of Rhachitomi have rhachitomous vertebrae; the largest subgroup, Stereospondyli, lacks pleurocentra. Below is a cladogram from Schoch's analysis showing the placement of Rhachitomi within Temnospondyli:
Laosuchus is an extinct genus of chroniosuchian known from the Permian-Triassic boundary of Asia. Two species have been named.
This list of fossil amphibians described in 2018 is a list of new taxa of fossil amphibians that were described during the year 2018, as well as other significant discoveries and events related to amphibian paleontology that occurred in 2018.
